Vultures of the seas: hyperacidic stomachs in wandering albatrosses as an adaptation to dispersed food resources, including fishery wastes.

Grémillet D, Prudor A, le Maho Y, Weimerskirch H - PLoS ONE (2012)

Bottom Line:
These revealed surprisingly low pH levels (average 1.50±0.13), markedly lower than in other seabirds, and comparable to those of vultures feeding on carrion.Such low stomach pH gives wandering albatrosses a strategic advantage since it allows them a rapid chemical breakdown of ingested food and therefore a rapid digestion.This is useful for feeding on patchy, natural prey, but also on fishery wastes, which might be an important additional food resource for wandering albatrosses.

ABSTRACTAnimals are primarily limited by their capacity to acquire food, yet digestive performance also conditions energy acquisition, and ultimately fitness. Optimal foraging theory predicts that organisms feeding on patchy resources should maximize their food loads within each patch, and should digest these loads quickly to minimize travelling costs between food patches. We tested the prediction of high digestive performance in wandering albatrosses, which can ingest prey of up to 3 kg, and feed on highly dispersed food resources across the southern ocean. GPS-tracking of 40 wandering albatrosses from the Crozet archipelago during the incubation phase confirmed foraging movements of between 475-4705 km, which give birds access to a variety of prey, including fishery wastes. Moreover, using miniaturized, autonomous data recorders placed in the stomach of three birds, we performed the first-ever measurements of gastric pH and temperature in procellariformes. These revealed surprisingly low pH levels (average 1.50±0.13), markedly lower than in other seabirds, and comparable to those of vultures feeding on carrion. Such low stomach pH gives wandering albatrosses a strategic advantage since it allows them a rapid chemical breakdown of ingested food and therefore a rapid digestion. This is useful for feeding on patchy, natural prey, but also on fishery wastes, which might be an important additional food resource for wandering albatrosses.

Mentions:
Using the first stomach pH recording ever conducted in a foraging petrel, we validate our prediction that the stomach pH of wandering albatrosses is extremely low (Fig. 2). Such low pH is very close to the baseline stomach pH recorded in white-backed griffon vultures (Fig. 3, [30]), and is significantly lower than pH levels recorded in a variety of other seabird species that mainly feed on fish and were previously studied using the same miniaturised, autonomous pH-meters (Fig. 3).

Mentions:
Using the first stomach pH recording ever conducted in a foraging petrel, we validate our prediction that the stomach pH of wandering albatrosses is extremely low (Fig. 2). Such low pH is very close to the baseline stomach pH recorded in white-backed griffon vultures (Fig. 3, [30]), and is significantly lower than pH levels recorded in a variety of other seabird species that mainly feed on fish and were previously studied using the same miniaturised, autonomous pH-meters (Fig. 3).

Bottom Line:
These revealed surprisingly low pH levels (average 1.50±0.13), markedly lower than in other seabirds, and comparable to those of vultures feeding on carrion.Such low stomach pH gives wandering albatrosses a strategic advantage since it allows them a rapid chemical breakdown of ingested food and therefore a rapid digestion.This is useful for feeding on patchy, natural prey, but also on fishery wastes, which might be an important additional food resource for wandering albatrosses.

ABSTRACTAnimals are primarily limited by their capacity to acquire food, yet digestive performance also conditions energy acquisition, and ultimately fitness. Optimal foraging theory predicts that organisms feeding on patchy resources should maximize their food loads within each patch, and should digest these loads quickly to minimize travelling costs between food patches. We tested the prediction of high digestive performance in wandering albatrosses, which can ingest prey of up to 3 kg, and feed on highly dispersed food resources across the southern ocean. GPS-tracking of 40 wandering albatrosses from the Crozet archipelago during the incubation phase confirmed foraging movements of between 475-4705 km, which give birds access to a variety of prey, including fishery wastes. Moreover, using miniaturized, autonomous data recorders placed in the stomach of three birds, we performed the first-ever measurements of gastric pH and temperature in procellariformes. These revealed surprisingly low pH levels (average 1.50±0.13), markedly lower than in other seabirds, and comparable to those of vultures feeding on carrion. Such low stomach pH gives wandering albatrosses a strategic advantage since it allows them a rapid chemical breakdown of ingested food and therefore a rapid digestion. This is useful for feeding on patchy, natural prey, but also on fishery wastes, which might be an important additional food resource for wandering albatrosses.